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Transfer Switching with Breakers ... In Less Than 2 Cycles

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A good transfer switch is able to transfer the load from an alternative source with zero or minimal loss of power. So far this can be achieved with static transfer switches, but the investment costs are substantial and there are technical limits due to the drastic short circuit constraints. For these reasons conventional medium voltage circuit breakers are still installed widely in power genera on plants and utilities.

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Transfer Switching with Breakers ... In Less Than 2 Cycles

  1. 1. Phone: 1.866.551.8362 (604.540.6600) Website: www.tavrida-na.com Office: 1105 Cliveden Ave, Delta, British Columbia, Canada ISM_Shell Series Breakers and Fast Transfer A good transfer switch is able to transfer the load from an alternative source with zero or minimal loss of power. So far this can be achieved with static transfer switches, but the investment costs are substantial and there are technical limits due to the drastic short circuit constraints. For these reasons conventional medium voltage circuit breakers are still installed widely in power generation plants and utilities. However due to the relatively slow opening and closing times of conventional circuit breakers, power is typically interrupted for more than 5 cycles, and even interruptions of 8 or more cycles are not uncommon. For industrial applications this can result in significant slowing down of motors, which produces a phase angle between the “lost source” and the alternative source. If the interruption is too long, the motor can be severely damaged. Thus many industrial systems actually do not perform “live transfer” in order to mitigate risks of losing expensive investments. At the same time any down-time of industrial processes or customer outages leads to significant costs or penalties. Tavrida Electric has revolutionized circuit breaker design by developing a new generation of circuit breakers and controls with exceptionally fast opening, closing and response times. This enables transfer times as fast as 2 cycles with the SEL 451 in a closed transition (“make before break”) and less than 3 cycles for an open transition (“break before make”). Transfer switching with breakers....in less than 2 cycles PT PT Breaker Control Breaker Control SEL-451 Breaker #1 Normally Closed Breaker #2 Normally Open Main Source Backup Source Motor Loads M M FAULT Transfer to Backup Source <2 Cycles • Complete power transfer in less than two cycles • Overcurrent protection for main source and backup • Implementation of breaker failure logic for both circuit breakers • Tracking of average and last circuit breaker oper- ating time • Setting of alarm or protect against system fre- quency voltage and frequency excursions using built-in voltages and frequency elements
  2. 2. Phone: 1.866.551.8362 (604.540.6600) Website: www.tavrida-na.com Office: 1105 Cliveden Ave, Delta, British Columbia, Canada ISM_Shell Series Breakers and Fast Transfer Fast Transfer Switch Package Component Description ISM15_Shell_2(FT) Shell type breaker, rated 15kV - 2000A - 25kA - 95kV BIL CM_1501_01(4) Breaker control module, 85 - 265 VAC / VDC input with 4 ms reaction time SEL-451® Schweitzer Engineering transfer switch relay assembly + options Timing Details Product Parameters Designation Response time Tavrida SHELL CB opening time (including fast control module response time) Topen 8 ms (<1/2 cycle) Tavrida SHELL CB interrupting time (including fast control module response time) Tinterrupt 16.3 ms (<1 cycle) Tavrida SHELL breaker closing time (including fast control module response time) Tclose 22 ms (1.32 cycles) SEL-451 Open Phase Detection Logic trip time TSEL451 10 ms (0.6 cycles) Transfer switch time closed transition “make-before-break” with SEL-451 Open Phase Detection Logic TSEL451+ Tclose 32 ms (<2 cycles) Transfer switch time open transition “break-before-make” with SEL-451 Open Phase Detection Logic TSEL451+ Tclose + Topen 40 ms (<2.5 cycles)

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